在 angular2 中订阅后，在执行下一行之前等待 Http 请求完成

Question

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class TextComp 
{

result: string;
constructor() {

    this.getdata().subscribe(result => {
        console.log("result received");
        this.result = result;
    });

    console.log("called before result received " + this.result);

    //this.result is NULL/UNDEFINED because this line executed before data received

    // So how we can eliminate this situation??? or
    // Is there any way to make synchronus call to http in angular 2
}

getdata() {
    return http.get('test.json')
        .map(response => response.json());
}
}

那么我们如何才能消除这种情况？？？ 或者有什么方法可以在angular 2中同步调用http

Answer 1

如果你需要在这种情况下进行同步调用，你的代码应该是这样的：

this.getdata().subscribe(result => {
    console.log("result received");
    this.result = result;
    //function or snippet which will be called after subscribe is complete...     
});

因为您的 subscribe 方法是异步工作的。 我建议你也看看promises 。